Apparatus for cataphoretic application of coatings



y ,1958 M. c. HOFFMAN 2,843,596

APPARATUS FOR CATAPHORETIC APPLICATION OF COATINGS Original Filed Sept. 50, 1949 Iii l/llllll lllllllwlll I I II, a

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INVENTOR MILTON C. HOFFMAN ATTORNEY United States Patent Ofiice 2,843,594 Patented July 15, 1958 APPARATUS FOR CATAPHORETIC APPLICATION OF COATINGS Milton C Hoffman, Emporium, Pa., assignor to Sylvania Electric Products, Inc., a corporation of Massachusetts Original application September 30, 1949, Serial No. 118,809, now Patent No. 2,699,426, dated January 11, 1955. Divided and this application August 31, 1954, Serial No. 453,263

5 Claims. (Cl. 204-299) The present invention relates to the application of coating material to conductive supports and more particularly to the cataphoretic coating of finely divided solid particles contained in a liquid suspension onto conductive supports.

An object of the present invention is the provision of a novel arrangement for coating emissive material. onto a filament.

A further object of the present invention is the avoidance of the substantial loss of coating material and coils due to imperfect masking or entangling of the coils, abraded and cracked coatings, and physical destruction due to handling difficulties which has characterized pre viously known methods of coating filament coils.

Still a further object of the present invention is the reduction in cost of coating emissive material onto coil filaments.

The foregoing objects and others which may appear from the following detailed description are attained in accordance with an aspect of the present invention by dipping the already coiled filament, attached to a conductive support into a vertically emergent stream or fountain of coating suspension discharging from a pumping device. An electrical potential is applied between an electrode in the body of the suspension and the conductive support immersed in the fountain thereof for a controlled period of time. As a result of the current which flows in the circuit thus established finely divided solid particles contained in the suspension attach themselves to the conductive support or to other like particles so attached and thus provide a closely adherent dense coating of material on the filament, said coating being substantially uniform and complete irrespective of the physical form of the conductive support.

The present invention will be more fully understood by reference to the following detailed description which is accompanied by a drawing in which Figure 1 illustrates in a perspective view an embodiment of the present invention while Figure 2 is an elevational view in section showing the interior construction of the device shown in Figure 1.

In the drawing there is shown a bath or tank containing a liquid suspension 12 of the desired finely ground coating material suspended in a solvent of high dielectric strength. Supported immediately above the bath 10 containing the suspension and dipping into the bath is an Archimedean pump including a vertical cylinder 14 having a rotating spiral 16 therewithin. The rotating spiral 16 is adapted to be rotated by shaft 17 driven by a suitable motor (not shown). Rotation of the spiral 16 causes the suspension 12 to be drawn up within the tube 14. Other forms of pumping devices may be used if desired. The liquid is discharged into a lateral tube 18 which connects with a vertically extending, vertically directed nozzle 20. A needle valve arrangement 22 is provided by means of which the volume and height of the stream emerging from the nozzle 20 may be controlled. In order to assure a continuous flow of the cataphoretic suspension from the bath 10, the upper end of tube 14 is provided with an overflow tube 24 by means of which surplus fluid not passing through tube 18 and nozzle is returned to the bath 10. The nozzle 20 extends through an aperture 26 in a table 28, preferably of insulating material. The coating material which emerges from nozzle 20 drops back through aperture 26 and falls into the bath 10. Thus a constant circulation of the coating suspension is provided.

The filament to be coated with the suspension is shown in Figure 1 at 30. It is previously assembled to a pair of support wires 32 and 34, one of the wires being connected to stem shield 36 of the amount while the other is insulatingly held in a position generally parallel to the first. A unitary mount assembly is thus provided which may subsequently have wires 32, 34 sealed through a header of an electron tube. A conductive seat is provided on table 28 so positioned that when the stem shield 36 is positioned in the support the filament 30 is supported directly above nozzle 20 and within the emergent jet or stream of material. The positioning of the stem shield 36 in the mount 40 depresses :an actuating leaf 42 of a normally open switch indicated generally at 44, whereby a circuit is completed from a source of potential as indicated by the arrow labeled to power supply through timer through the closed contacts of switch 44, the base shield supporting member 40, base shield 36, one of the conductors 32, 34, filament 39, through the jet of coating material emerging from nozzle 20 and through the remainder of the coating suspension material or the metal tubes 18, 14 to the other side of the power supply, as mentioned before the straight filament coil 30 of the otherwise completed mount is positioned by the mounting support 40 acting as a jig so that the emergent jet of coating suspension material from nozzle 20 covers the portions of the coil to be coated. This positioning is substantially mechanically controlled as the operator places the mount in the jig. Placing the mount in the jig also actuates the electrical switch 44 which provides for the closing of the electrical circuit for an accurately determined time period controlled by the timer 45. At the end of the time period the completed mount is removed from the coating device and immediately the filament coil is dipped momentarily in a solution of diethylcarbonate to effect the removal of the excess nonadherent coating and finally in petroleum ether to complete the removal of excess material and to accelerate the subsequent air-drying. I have found that the time period of the coating application will vary to some extent with the particular suspension and the coating thickness requirement, but the time interval on the order of one-and-a-half seconds has proved satisfactory. The subsequent rinsing operations normally are accomplished in time periods of one-half to three seconds each.

While the coating suspension may be any suspension of finely divided solid particles in a solvent. of high dielectric strength such that movement of the solids occurs with an impressed potential, I prefer that the suspension should be one of the varieties indicated in prior Patents 2,442,863 and 2,442,864.

While I have shown and particularly described one embodiment of the present invention, it should be clearly understood that my invention is not limited thereto but that modifications within the scope of the claims may be made.

This applicaion is a division of application Serial No. 118,809, filed September 30, 1949, now Patent 2,699,426, granted January 11, 1955.

What I claim is:

1. A device for applying electrophoretic coating material to conductors including a nozzle having a narrow elongated slot for projecting a jet of liquid suspension of said material, a support adjacent to said nozzle and to one side thereof, for positioning said conductor within said jet with the elongation of the conductor parallel with the elongated slot of the nozzle and means for applying a potential difference between said material and said conductor, said support including a non planar seat having an elongation which is within the axis of the narrow elongated slot for assuring the correct positioning of said conductor within said jet and a switch responsive to the correct placement of said conductor for applying said potential dilference to said material and said conductor.

2. A device for electrophoretically applying a coating to an elongated coil filament carried by a mount including a pair of supporting wires and a shield connected to one of said wires, comprising a nozzle having a narrow elongated slot for projecting a jet of a liquid suspension of said material, a seat adjacent said nozzle for receiving said shield so positioned that said filament is alined with the slot of said jet, and a switch having an acutating arm normally above the level of the bottom of the seat adjacent said seat whereby placement of said shield in said seat actuates said switch, said switch being connected in a circuit with a timer for passing a current through said filament and said jet for a predetermined time interval.

3. A device for electrophoretically applying a coating to an elongated coil filament carried by a mount including a pair of supporting wires and a circular shield connected to one of the wires, comprising a nozzle for projecting a jet of a liquid suspension of said material, an arcuate seat adjacent said nozzle for receiving said shield so located that said filament is over the nozzle when the shield is positioned in the seat, and a switch having an actuating leaf normally above the level of the bottom of said seat and in the path of movement of the shield to its seat, said switch being connected in a circuit with a timer for passing a current through said filament and said jet for a predetermined time interval.

4. A device for electrophoretically applying a coating to an elongated coil filament carried by a mount including a pair of supporting wires and a circular shield connected to one of the wires, comprising a nozzle having a narrow elongated slot for projecting a jet of a liquid suspension of said material, an arcuate seat adjacent said nozzle for receiving said shield so located that said elongated filament is over .and parallel with the elongated nozzle when the shield is positioned in the seat, and a switch having an actuating leaf normally above the level of the seat and in the path of movement of the shield to its seat, said switch being connected in a circuit with a timer for passing a current through said filament and said jet fora predetermined time interval.

5. A device for electrophoretically applying a coating to a filament carried by a mount including a pair of supporting wires and a circular shield connected to one of the wires, comprising a nozzle for projecting a stream of a liquid suspension of said material, a circular seat for said shield close to but displaced laterally of the nozzle and out of the path of the stream issuing from the nozzle and so located that said filament is over the nozzle when the shield is positioned in said seat, and a switch having an actuating means normally above the level of the seat and in the path of movement of the shield to its seat, said switch being connected in a circuit with a timer for passing a current through said filament and said stream for a predetermined time interval.

References Cited in the file of this patent UNITED STATES PATENTS 1,416,929 Bailey May 23, 1922 1,911,808 Collins May 30, 1933 2,035,633 'Bogle Mar. 31, 1936 2,374,088 Fontana et a1. Apr. 17, 1945 2,431,629 Wind Nov. v25, 1947 2,532,907 Hangosky Dec. 5, 1950 2,744,061 De Ford May 1, 1956 FOREIGN PATENTS 901,563 France Nov. 6, 1944 

1. A DEVICE FOR APPLYING ELECTROPHORETIC COATING MATERIAL TO CONDUCTORS INCLUDING A NOZZLE HAVING A NARROW ELONGATED SLOT FOR PROJECTING A JET OF LIQUID SUSPENSION OF SAID MATERIAL, A SUPPORT ADJACENT TO SAID NOZZLE AND TO ONE SIDE THEREOF, FOR POSITIONING SAID CONDUCTOR WITHIN SAID JET WITH THE ELONGATION OF THE CONDUCTOR PARALLEL WITH THE ELONGATED SLOT OF THE NOZZLE AND MEANS FOR APPLYING A POTENTIAL DIFFERENCE BETWEEN SAID MATERIAL AND SAID CONDUCTOR, SAID SUPPORT INCLUDING A NON PLANAR SEAT HAVING AN ELONGATION WHICH IS WITHIN THE AXIS OF THE NARROW ELONGATED SLOT FOR ASSURING THE CORRECT POSITIONING OF SAID CONDUCTOR WITHIN SAID JET AND A SWITCH RESPONSIVE TO THE CORRECT PLACEMENT OF SAID CONDUCTOR FOR APPLYING SAID POTENTIAL DIFFERENCE TO SAID MATERIAL AND SAID CONDUCTOR. 